The present invention relates to an improved process for producing plastically deformable, or malleable, white cast iron. The process advantageously allows for the manufacture of products heretofore impracticable using conventional methods, e.g., products (such as approximately 2 mm thick sheet, or wire having a diameter of approximately 2 mm) resulting from deformation using high reduction ratios during manufacture.
When alloyed with known carbide formers, white cast iron tends to exhibit high hardness and wear resistance, but often has less than desirable mechanical performance characteristics and low fatigue strength. Further, notwithstanding such properties, commercial scale plastic deformation of such white cast iron often is constrained due to a relatively low deformability of the material, which is believed to be caused by the presence in its structure of a eutectic-formed brittle phase.
One process for producing deformable white iron is described in Yu.N. Taran, et al. "Deformable Moderately Alloyed White Irons" in Metallovedenie i termicheskaya obrabotka metallov, 1989, No. 4, pp. 35-43. The process is believed to involve alloying iron with chromium and vanadium, which are dissolved in eutectic cementite, to make the latter oversaturated and soluble during further annealing and plastic working.
This process however, is believed to be limited because it does not control specific microstructural transformations, and thus is not believed to be commercially practicable. For instance, plastic deformation of this iron is believed to be possible only within a narrow temperature range, which is difficult to achieve and maintain for commercial scale deformation.
Another process for producing deformable white iron is disclosed in DE,1287593. According to that process, a material is prepared containing, by weight, 1.7 to 3.8 percent carbon; 0.4 to 2.5 percent silicon; less than 1.0 percent manganese; less than 2.0 percent chromium; less than 2.0 percent molybdenum; less than 1.0 percent vanadium; less than 1.0 percent tungsten, with the balance being iron. The process is believed to require heating an ingot to a temperature which is 50.degree. C. below the solidus temperature and carrying out plastic deformation in a temperature range of 900.degree. to 1125.degree. C. The plastically deformed ingot is subsequently slow cooled.
The above mentioned process allows for large-size rolls to be press formed from white cast iron ingots. However, the process is believed to be limited to low amounts of deformation and low deformation rates.